Of all the nutrients in the food supply, fat and cholesterol probably receive the most attention from health professionals and the public alike. Dietary recommendations from health experts advise lowering the total fat, saturated fat, and cholesterol in our diets. The scientific evidence is clear that a high-fat diet relates to chronic health problems such as heart disease, some types of cancer, diabetes, and obesity.

Books, cookbooks, and magazine articles tout low-fat messages. The food industry continues to provide reduced-fat and fat-free food products. Both fat and cholesterol are natural components of the body that are vital to good health, but too much fat or the wrong fat in the diet can rob you of good health. Too little fat in your diet is just as unhealthy as too much, especially for children. This article will review dietary fats and provide guidelines for choosing foods to balance the type and amount of fat in your diet.

What is the role of fat in the diet?

Fat has qualities that make food taste good. It delivers flavor from foods, and provides aroma. It also gives a smooth, creamy texture to many foods like ice cream, chocolate and peanut butter. Fat also makes foods such as meat and baked goods moist and tender or brown and crispy.

Fat is important for slowing the digestive process so you are not hungry an hour after eating a meal. Fat also adds satiety and a sense of fullness after eating a meal. One role of fat in the diet is to aid in the absorption of fat-soluble vitamins, which include vitamins A, D, E, and K.

What is fat?

Fat is the most concentrated source of energy in the diet, providing nine calories per gram while carbohydrates and protein have only four calories per gram. Fat accounts for about 34% of our calorie intake in the United States.

Fat has three elements: carbon, hydrogen and oxygen. However, fats have more carbon and hydrogen and lessoxygen, thus yielding nine calories per gram. Fats are known as triglycerides, both in food and in the body.

Each triglyceride can be broken down into three fatty acids plus glycerol. Fatty acids are arranged as chains. Each fatty acid from a triglyceride is classified as a saturated (SFA), a monounsaturated (MUFA) or a polyunsaturated (PUFA) fatty acid. Triglycerides are mixtures of the three different types of fatty acids, SFA, MUFA and PUFA; the proportion of each determines the characteristics of fats in food and their effect on human health. All fats provide 9 calories per gram.

What are essential fatty acids?

The human body can make all but two fatty acids, linoleic acid and linolenic acid. Because these two fatty acids are essential to body function, they must be obtained from the diet. Therefore, they are called essential fatty acids. These essential fatty acids are used as parts of cell membranes and in the synthesis of hormone-like substances.

Linoleic acid is an omega-6 fatty acid and it is the primary essential fatty acid in the diet. The body uses linoleic acid to make arachidonic acid, which is the form that is used in the body for synthesis of the hormone-like compounds that are essential for blood pressure regulation, blood clot formation, blood lipid synthesis, and immune response to injury and disease.

Linolenic acid is an omega-3 fatty acid. The body can make eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from linolenic acid. EPA and DHA are important for normal growth and development in children. Without these fatty acids, children would not grow normally. EPA and DHA are also active in brain and eye development. These fatty acids may also be important in the prevention and treatment of heart disease, hypertension, arthritis, and cancer, especially in adults. EPA and DHA are also used by the body to make hormone-like compounds which are essential to many functions. They include immune response to injury and infection, blood lipid synthesis, blood clot formation and blood pressure regulation.

SFA: Saturated fats are usually solid or firm at room temperature. Animal foods and the tropical oils have a higher percentage of SFA than do most other plant foods. The fats in beef tallow, pork, lard, lamb, poultry skin, butterfat, and egg yolk are mostly saturated. Plant fats with a high content of SFA include tropical oils like coconut oil, palm kernel oil, cocoa butter, and palm oil. SFA can increase blood cholesterol levels. Higher levels of blood cholesterol increase the risk of heart disease.

PUFA: Foods high in PUFA are liquid at room temperature. Foods high in PUFA include corn oil, safflower oil, soybean oil, sunflower oil, cottonseed oil, walnuts, margarines made with high PUFA oils, and seafood.

MUFA: Oils high in MUFA are liquid at room temperature. Examples of foods high in MUFA are olives, olive oil, canola oil, peanuts, peanut oil, almonds, pecans, hazelnuts, cashew nuts, macadamia nuts, pistachio nuts, and avocados. Eating foods high in MUFA will also help lower blood cholesterol, but does not lower HDL-cholesterol, the "good"cholesterol

MUFA and PUFA both have a blood-cholesterol lowering effect and can lower the risk of heart disease. Reducing total fat and replacing some saturated fat with unsaturated fats can help lower your risk of heart disease. Eating foods high in PUFA can help lower blood cholesterol but may lower HDL-cholesterol, the "good" cholesterol.

What are hydrogenated and trans fats in the diet?

Unsaturated fats can be made more saturated by adding hydrogen. The process is called hydrogenation. The result is oils becoming more solid and stable at room temperature. A good example is stick margarine, made by hydrogenating vegetable oil. This process increases the stability of fats; therefore, the shelf life is increased.

Trans-fatty acids are formed during the process of hydrogenation. Trans-fatty acids, as well as hydrogenated fats raise blood cholesterol which raises the risk for heart disease.

To reduce your trans-fatty acid intake, eat less fat, choose softer tub margarines, and use oil for cooking and salad dressings. Read food labels and avoid products with hydrogenated fats. This can also help lower your intake of trans-fatty acids.

What is the role of cholesterol in the diet?

Cholesterol, a waxy fat-like substance, is found in every body cell. Cholesterol is necessary for nerve cell function, sex hormone production and the production of vitamin D from sunlight exposure of the skin. Humans can generally make all the cholesterol they need withoutfood sources. Cholesterol is only found in animal foods.

The American Heart Association and the National Cholesterol Education Program recommends limiting cholesterol intake from food to 300 mg per day.

Table 2. Sources of Cholesterol and Fat in the Diet

Foods

Cholesterol (mg)

Fat (g) serving

Beef top sirloin lean (3 oz.)

76

7

Ground beef, reg (3 oz.)

77

18

Veal sirloin

93

9

Hot dog (1)

29

13

Chicken leg w/skin

105

16

Chicken leg w/o skin

90

8

Chicken breast w/ skin (3 oz.)

82

8

Chicken breast w/o skin (3 oz.)

73

3

Organ meat (3 oz.)

--Brains

1760

11

--Liver

333

4

--Kidneys

332

3

Shrimp (3 oz.)

166

1

Lobster (3 oz.)

61

1

Clams (3 oz).

57

2

Oysters (3 oz.)

85

4

Fish, cod (3 oz.)

47

1

Egg yolk

218

5

Ice cream, 16% fat (1 cup)

90

24

Whole milk (1 cup)

35

9

Cheddar cheese (1 oz.)

30

9

Croissant, 1 medium

43

12

Doughnut, yeast glazed

14

4

Brownie, large (2 oz.)

10

9

Chocolate, Hershey's (1 oz.)

2

8

Olive, large ripe (5)

0

3

Avocado, Calif. (1 med.)

0

30

Peanut butter, crunchy (2 Tbsp)

0

16

Almond butter (2 Tbsp)

0

19

What are the recommended intakes of fat in the diet?

The National Cholesterol Education Program (NCEP) recommends that all healthy Americans, 2 years and older, adopt an eating pattern which is lower in saturated fat and cholesterol to lower their blood cholesterol. According to the American Academy of Pediatrics, optimal fat intake for children is unknown; however, 30 percent of calories from fat seems sensible for adequate growth and development.

less than 10 percent of calories from saturated fat.

an average of 30 percent of calories or less from total fat.

less than 300 mg a day of dietary cholesterol.

Other recommendations include:

10 percent or less of total calories from polyunsaturated fat intake

10 to 15 percent of total calories from monounsaturated fat

balance omega-3 and omega-6 fatty acid intake with a ratio of 1 part omega-3 to 4 parts omega-6 fatty acids (see Table 1 for lists of food sources of these fatty acids).

How can you meet the recommended fat intakes?

Meal PlanningPlanning meals to meet the recommended fat intakes doesn’t have to be complicated. Here are a few suggestions:

Choose fish, poultry, and lean cuts of meat, and remove the fat and skin before cooking. Eat no more than 6 ounces per day. Or substitute vegetarian sources of protein for animal sources several times a week. Good sources include soybeans or soy foods and other high protein plant sources such many types of beans.

Broil, bake, roast, or poach foods rather than fry them.

Cut down on high fat processed meats, including hot dogs, sausage, bacon, spare ribs, and such cold cuts as salami and bologna.

Limit organ meats such as liver, kidney, or brains.

Use skim or low-fat milk, cheeses, and yogurt.

Use liquid or soft tub margarines or vegetable oils high in monounsaturated fats like canola and olive oil instead of butter. Choose margarine containing liquid vegetable oil as the first ingredient. Use all fats and oils sparingly.

Eat egg yolks in moderation; no more than 3 or 4 per week. Egg whites contain no fat or cholesterol and can be included as a good protein source. Two egg whites are equivalent to 1 ounce of meat for protein.

Eat plenty of fruits and vegetables, as well as cereals, breads, rice and pasta made from whole grains.

Go easy on packaged and processed foods, such as pies, cakes, cookies, doughnuts, croissants, and muffins, that are high in saturated or hydrogenated fats.

Get in the habit of reading food labels. Look for the “Nutrition Facts” on the label and choose products that are lowest in fat and saturated fat. Also avoid products that list hydrogenated fats high on the ingredient list.

Recipe Changes: Here are some changes to try in recipes to decrease fat content which will help meet recommended fat intakes:

If recipe calls for:

Use:

whole milk

skim milk

margarine

light or fat-free margarine

mayonnaise

reduced fat or fat-free mayonnaise

cream cheese

light or fat-free cream cheese or fat-free ricotta cheese

whole milk ricotta

part skim or fat-free ricotta

regular cheese

part skim or reduced fat cheese

whole egg

two egg whites

whipping cream

non-fat yogurt, or whipped topping made with skim milk

Other suggestions to modify recipes to decrease fat in cooking:

Try cutting oil or fat by one-fourth or one-half.

Substitute lean meats for fattier cuts of meat.

In casseroles or stir-fry dishes, use more vegetables and less meat, decrease fat in sauces and use nonstick cookware for stir-frying.

Portion Sizes: Decrease fat in the diet by decreasing portion sizes of meat: a lean 3 ounce meat portion provides the nutrients you need for lunch or dinner and is approximately the size of a deck of cards. Eat high fat foods less often and in smaller portions.

Is there a minimum amount of fat that we need to be healthy?

Fat is a nutrient that is necessary for health. Fat performs a number of essential functions in the body. For these reasons a fat-free diet is not recommended. You need at least 10 to 20 percent of your overall calories as fat according to the Food and Agriculture Organization/World Health Organization.

Table 3. Sources of Omega Fatty Acids

WHO

TOTALCALORIES

CALORIESFROM FAT

GRAMSOF FAT

TSP OF FAT

Active adult male

2,500-2,000

750-900

83-100

17-20

Adult male or active female

2,000-2,500

600-750

67-83

1 3-17

Adult female or elderly male

1,500-2,000

450-600

50-67

10-13

Dieting adult or elderly female

1,000-1,500

300-450

33-50

6 -10

Table 4. Food Label Terms for Fat

Fat-free

Less then 0.5 grams per serving size listed on the label.

Low-fat

3 grams or less per serving.

Reduced or less fat

At least 25 percent less per serving than the reference food.

Saturated fat-free

Less than 0.5 grams saturated fat and less than 0.5 grams trans fatty acids per serving.

Low saturated fat

1 gram or less per serving and not more than 15 percent of the calories from saturated fatty acids.

Reduced or less saturated fat

At least 25 percent less per serving than the reference food.

Cholesterol free

Foods which contain less than 2 milligrams of cholesterol per serving and 2 grams or less of saturated fat per serving.

Low cholesterol

Foods with less than 20 milligrams of cholesterol per serving and 2 grams or less of saturated fat per serving.

Cholesterol reduced

Foods that have no more than one-quarter (25%) of the cholesterol content of the foods for which they substitute and that they resemble in taste and flavor. These products provide information on how the new product compares with the one it replaces.

Facts About Heart Disease and Women: Reducing High Blood cholesterol, U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, National Heart, Lung and Blood Institute. July 1994 Sorting Out the Facts About Fat, IFIC Review, International Food Information Council, Washington, D.C. May 1991

The University of Arizona is an Equal Opportunity/Affirmative Action Employer. Any products, services, or organizations that are mentioned, shown, or indirectly implied in this publication do not imply endorsement by the University of Arizona.Document located http://cals.arizona.edu/pubs/health/az1126.htmlPublished August 1999